Enable feature for example custom_3d_glow (#7730)

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examples/custom_3d_glow/Cargo.toml

@@ -14,6 +14,7 @@ workspace = true
 [dependencies]
 eframe = { workspace = true, features = [
   "default",
+  "glow",
   "__screenshot", # __screenshot is so we can dump a screenshot using EFRAME_SCREENSHOT_TO
 ] }
 env_logger = { workspace = true, features = ["auto-color", "humantime"] }